Five characteristics, including extreme mood swings and psychiatric symptoms at a young age, may help pinpoint which patients actually have bipolar disorder, they say.

Bipolar disorder covers a spectrum of disorders in which patients may be sad and down one day and feeling on top of the world, hyperactive, creative, and grandiose the next.

The extreme mood swings may be more or less frequent and more or less severe, says study head Charles Bowden, MD, of the University of Texas Health Science Center in San Antonio. Bowden has consulted for Sanofi-Aventis, which funded the study.

"As a result, bipolar disorder can be difficult to diagnose, even by experienced psychiatrists," he tells WebMD.

Recent studies suggest as many as 40% of patients receive another diagnosis first and that it can take years before they're correctly diagnosed, Swanson says. Many are diagnosed with major depression, resulting in inappropriate use of antidepressants, he says.

Not only do antidepressants fail to help, "but patients can get worse, their mood can become more unstable, and some even get more manic," says Donald Hilty, MD, co-chair of the committee that chose which studies to highlight at the meeting and professor of psychiatry at the University of California, Davis.

These patients should be on a mood-stabilizing drug, he tells WebMD.

The current study involved 5,635 patients with major depression from 18 countries in Europe, Asia, and North Africa.

The researchers sought to determine which patients fit the criteria for bipolar depression using various tools, and see which factors best predicted a diagnosis of bipolar disorder.

5 Factors Associated With Bipolar Disorder

The findings were presented at the annual meeting of the American Psychiatric Association.

"What we found," Swanson says, "is that five items are associated with bipolar disorder."

About 29% of the patients in the study were determined to have bipolar disorder, Swanson says.

Using the DSM-IV, the bible for psychiatric diagnoses, 31% fulfilled criteria for bipolar disorder.

And using new criteria that takes into the five risk factors proposed by Swanson, 47% had bipolar disorder.

"Our findings suggest that about one-third of people with major depression have [undiagnosed bipolar disorder]," Swanson says. "Currently patients have to have elevated mood or irritability before we can even consider a diagnosis of bipolar disease. Our findings suggest that may not always be the case."

"This is an excellent study that is clinically useful, giving us information we can use right away," Hilty says.

"It's really important that we understand predictors of bipolar disorder as it is still underdiagnsoed as regular depression, he tells WebMD.

This study was presented at a medical conference. The findings should be considered preliminary as they have not yet undergone the "peer review" process, in which outside experts scrutinize the data prior to publication in a medical journal.

SOURCES:163rd Annual Meeting of the American Psychiatric Association, New Orleans, May 22-26, 2010.Charles Bowden, MD, University of Texas Health Science Center, San Antonio.Donald Hilty, MD, co-chair, program committee, 163rd Annual Meeting of the American Psychiatric Association; professor of psychiatry, University of California, Davis.